Three-position pneumatic or hydraulic power cylinder

ABSTRACT

The invention relates to hydraulic cylinder devices and can be used in vehicle transmissions. A three-position pneumatic or hydraulic cylinder consists of a housing having end caps, two pistons, a rod, and supply channels for a working fluid, each piston being configured for limited movement along the rod as a result of a central protuberance, which separates the pistons, and peripheral protuberances on the rod, and being configured for limited movement inside the housing. The central protuberance is configured in the form of a bushing, and an annular protuberance is, configured on the inside surface of the housing. Said bushing and said protuberance form a hermetic moveable coupling of the shaft/opening type. Separate channels are provided for supplying working fluid to the chambers formed by each piston and the corresponding end of the housing, and a shared channel is provided for supplying working fluid to the chambers formed by each piston and the central protuberance and bushing; or, separate channels are provided for supplying working fluid to the chambers formed by each piston and the central protuberance and bushing, and a shared channel is provided for supplying working fluid to the chambers formed by each piston and the corresponding end of the housing.

FIELD OF THE INVENTION

The invention relates to volumetric pneumatic or hydraulic drives, and more specifically to pneumatic (hydraulic) hydraulic cylinder devices and can be used in robotic production lines, drives of various purpose machines including in vehicle transmissions.

PRIOR ART

For example, a synchronizer shifting hydraulic drive is known (Patent RU2545543C2). The drive comprises a cylinder and piston arranged to move inside the cylinder separating the first and second chambers.

The first chamber volume is the smallest when the drive is in a first engagement position and the second chamber volume is the smallest when the drive is in a second engagement position. The piston also delimits the third chamber in the cylinder, which volume is the smallest when the drive is in a neutral position.

This drive is technologically complex product, in particular, its performance directly depends on the accuracy of pressurization in a particular chamber.

A three-position hydraulic cylinder is known (Patent RU2079007C1) comprising a housing with windows for load connection and working fluid supply, in which cavity closed by covers a bored piston and plungers interacting with it and covers are located wherein the plungers are located in the piston bore that is equipped with stops limiting its stroke.

A pin located perpendicular to the longitudinal axis of the body is used as a working, element interacting with the load. The disadvantage of this design is an inability to move the working element to the ends of housing.

A three-position pneumatic cylinder (Patent HU87364B3) was chosen as a prototype that consists of a housing having end caps, two pistons, a rod, channels for a working fluid. The pistons divide the interior of the cylinder into three chambers, wherein each piston is configured for, limited movement along the rod as a result of a central protuberance, which separates the pistons and peripheral protuberances on the rod, and configured for limited movement inside the housing as a result of the protrusions formed on the inside surface of the housing. A stop element is fixed on the rod between two pistons whereon an inlet port of the working fluid (air) supply channel to the chamber between the pistons.

The disadvantages of the known prototype device are the following design features:

Large dimensions due to the presence of the upper end cap.

Inability to implement additional rod outlets from one of the cylinder end surfaces and, for example, a perpendicularly installed pin.

The end surface of the protuberance (bushing) on the rod (in the working fluid supply area) acts as a piston and, therefore, affects any rod movement, that is, to set the rod to medium or neutral position an additional amount of energy (pressure) of the working fluid should be required.

The potential pressure difference when the rod is in the middle position may result in the so-called rod run-out beyond the middle position followed by return (travel) to the middle position. This factor is adverse in devices where this should not be according to the work functions.

Rod alignment is ensured by its contacts with covers and pistons that, with significant rod loading, an affect the uninterrupted operation time of the device. Alignment at seal points looks at least doubtful. HU87364B provides for increased piston fitting dimensions ensuring the rod alignment and this increases the device dimensions, weight and material consumption.

A more complex manufacturing design is used, for example, a retaining protuberance in the middle of the bushing shall be specifically fit relative to the working fluid outlet or have a evidently complex design with a system of grooves and holes while ensuring impact strength; the use of retaining rings also complicates the design; an additional upper end cap is used that shall be secured and sealed.

SUMMARY OF THE INVENTION

The object of the invention was to provide a device that is free of the above disadvantages. The technical result is a design simplification and improved reliability, speed and accuracy of the device.

This problem is solved by a three-position pneumatic or hydraulic cylinder that consists of a housing having end caps (walls), two pistons, a rod, channels for a working fluid wherein each piston is configured for limited movement along the rod as a result of a central protuberance, which separates the pistons, and peripheral protuberances on the rod, and for limited movement inside the housing wherein it is proposed that the central protuberance is configured in the form of a bushing, and an annular protuberance is configured on the inside surface of the housing wherein the bushing and protuberance form a hermetic moveable coupling of the shaft/opening type. In fact, the proposed solution results in a formation of four chambers inside the housing formed by end caps (walls), two pistons and a partition formed by a bushing and annular protuberance.

A protuberance is understood to mean any part such as a bushing, part of the housing or rod that limits the piston movement.

EMBODIMENT OF THE INVENTION

Two preferred embodiments of the invention are proposed determined by the implementation of the working fluid supply channels.

In the first preferred embodiment, the working fluid supply channels are implemented as follows: separate channels to the chambers formed by each piston and the corresponding end (end cap) of the housing, and a shared channel to the chambers formed by each piston and the central protuberance and bushing.

In the second preferred embodiment, the working fluid supply channels are implemented as follows: separate channels to the chambers formed by each piston and the central protuberance and bushing, and a shared channel to the chambers formed by each piston and the corresponding end (end cap) of the housing.

All embodiments may be supplemented by locating at least one load interacting pin inclined to the rod axis in the bore of the annular protuberance.

In one device embodiment, only the above pin element is provided for load interaction. In principle, a design may be implemented with one or two rod outlets, one or more pins in various combinations depending on the specific purpose of the device. The bushing with the pin may also rotate sectorally around the bushing axis.

The invention is illustrated by graphic materials: a prototype drawings and photographs.

FIG. 1 shows a longitudinal sectional view of a first preferred embodiment of a cylinder, central (middle) position.

FIG. 2 shows a longitudinal sectional view of a first preferred embodiment of a cylinder, rightmost position.

FIGS. 3 and 4 show a longitudinal sectional view of a second preferred embodiment of a cylinder, the central (middle) position with different design of the working fluid supply channels.

FIG. 5 shows a longitudinal sectional view of a second preferred embodiment of a cylinder, rightmost position.

FIG. 6 shows a general view of a prototype three-position cylinder with two end rod elements.

FIG. 7 shows an exploded view of a prototype three-position cylinder with two end rod elements.

FIG. 8 shows an exploded view of a prototype three-position cylinder with one end rod element.

A three-position cylinder consists of a housing 1 where the rod is located including the central part that a cylindrical bushing 2 with two protuberances for pistons 3 and 4 having free play both inside the cylindrical part of the housing 1 and on the bushing 2, two end caps 5 and 6, end rod elements 7, 8 and side pin 9. Preferably, the rod consists of several rigidly connected parts: bushing 2 made of a low friction sliding material, end parts 7, 8 with peripheral protuberances and side pin 9. The device also comprises working fluid (compressed air or liquid) supply channels A, B and C.

In the first preferred embodiment (FIGS. 1 and 2 ), separate channels A and C to the chambers formed by each of the pistons 3, 4 and the corresponding end of the housing (caps 5 and 6) can be provided in the housing and caps 5 and 6. The shared channel B to the chambers formed by each of the pistons 3, 4 and the central protuberance and bushing 2 can be provided in the protuberance of the housing 1.

In the second preferred embodiment (FIGS. 3, 4, 5 ), separate channels A and C to the chambers formed by each of the pistons and the central protuberance and bushing, is provided in the protuberance of the housing 1, and the shared channel B to the chambers formed by each of the pistons 3, 4 and the corresponding end (end caps 5, 6) can be provided in the wall of the housing 1 (FIGS. 3 and 5 ), or in the bushing 2 (FIG. 4 ).

The device is operable with any number of output load interacting elements (end elements 7, 8, pin 9). When using the device without end element(s) 7, 8, a protruding piston stroke limiter (pistons 3, 4) shall be installed on the bushing 2 and cap (caps 5, 6) with no rod holes. A prototype device with one end rod element is shown in FIG. 8 .

The device operation according to the first preferred embodiment (compressed air) is as follows.

When compressed air is supplied to channel B, piston 3 moves to the left, and piston 4 moves to the right, the pistons reach the protuberances of the caps 5, 6 and rest against the retaining protuberances of the rods 7 and 8 to, set the bushing 2 in the middle position (FIG. 1 ). Channels A and C are open to the atmosphere at that moment.

When compressed air is supplied to channel A, piston 3 moves to the right and, having reached the protuberance of the bushing 2, pushes it to the right, then the piston 3 rests against the retaining protuberance of the main housing, and the bushing 2 rests against the piston 4 that rests against the cap 6, thereby the bushing 2 with elements 7, 8 and pin 9 is set to the rightmost position (FIG. 2 ). Channels B and C are open to the atmosphere at that moment.

Movement to the leftmost position is made in the opposite (mirror) order relative to the movement to the rightmost position.

If the main housing, protuberances of end caps 5, 6 and bushing 2 have asymmetrical design, the rod may be retained in the required (shifted) intermediate position relative to the central (middle) position.

The device operation according to the second preferred embodiment (compressed air) is as follows (FIGS. 3, 4 ).

The device is also operable with any number of output load interacting elements (end elements 7, 8, pin 9). When using the device without end element(s) 7, 8, a protruding piston stroke limiter (pistons 3, 4) shall be installed (as in the first preferred embodiment) on the bushing 2 and cap (caps 5, 6) with no rod holes (FIG. 8 ).

When compressed air is supplied to channel B, piston 3 moves to the right, and piston 4 moves to the left, the pistons reach the protuberances of the bushing 2 and rest against the housing to set the bushing 2 with rods 7, 8 and pin 9 in the middle position. Channels A and C are open to the atmosphere at that moment.

When compressed air is supplied to channel C, piston 4 moves to the right and, having reached rod 8, moves the bushing 2 to the right, the rod 7 rests against piston 3, and the bushing 2 with rods 7, 8 and pin 9 is set to the rightmost position. Channels A and B are open to the atmosphere at that moment.

Movement to the leftmost position is made in the opposite (mirror) order relative to the movement to the rightmost position.

If the main housing 1 and bushing 2 have asymmetrical design, the rod may be retained in the required (shifted) intermediate position relative to the central (middle) position.

The operation principle of the device under liquid pressure is similar to the operation with compressed air but the channels of the main liquid lines that are not under high pressure at the rod repositioning shall open to the main low-pressure liquid line and expansion tank.

INDUSTRIAL APPLICABILITY

The prototype device (without pin 9 FIGS. 6, 7, 8 ) during testing demonstrated the operational capability, solved the problem and achieved the said technical result.

No failures, partial engagement and interruptions recorded during trial operation. It should also be noted that when any of three said positions is reached, the rod (and/or pin) driving (moving) force is the same, therefore it is valid to say that the cylinder is a power cylinder if ensured that all three positions are reached. The driving (moving) device is also operable with a to joint tightness but to ensure force retention in the reached position (under the working fluid pressure) appropriate tightness and sealing in the pistons and end caps shall be provided. 

1. A three-position pneumatic or hydraulic cylinder consisting of a housing having end caps, two pistons, a rod, and supply channels for a working fluid, each piston being configured for limited movement along the rod as a result of a central protuberance, which separates the pistons, and peripheral protuberances on the rod, and being configured for limited movement inside the housing wherein the central protuberance is configured in the form of a bushing, and an annular protuberance is configured on the inside surface of the housing wherein the bushing and protuberance form a hermetic moveable coupling of the shaft/opening type.
 2. A three-position cylinder according to claim 1 wherein the working fluid supply channels are implemented as follows: separate channels to the chambers formed by each piston and the corresponding end of the housing, and a shared channel to the chambers formed by each piston and the central protuberance and bushing.
 3. A three-position cylinder according to claim 1 wherein the working fluid supply channels are implemented as follows: separate channels to the chambers formed by each piston and the central protuberance and bushing, and a shared channel to the chambers formed by each piston and the corresponding end of the housing.
 4. A three-position cylinder according to claim 1, wherein at least one load interacting pin inclined to the rod axis is located in the bore of the annular protuberance.
 5. A three-position cylinder according to claim 2, wherein at least one load interacting pin inclined to the rod axis is located in the bore of the annular protuberance.
 6. A three-position cylinder according to claim 3, wherein at least one load interacting pin inclined to the rod axis is located in the bore of the annular protuberance. 